Neighbours and the Invercargill City Council have been trying since 2011 to persuade Gardiner to give up most or all of her estimated 25 or 26 cats.
Last year she was charged with breaching a council bylaw by failing to comply with a notice instructing her to reduce the number of cats to no more than three, and also faced a Health Act charge of allowing cats to create a nuisance.
After a judge-alone trial, Judge David Saunders told Gardiner: ''The time has come for reality to sink in'', convicting her, fining her, and ordering her to dispose of all her cats bar three.
Sarah McKenzie, who appeared for the council, said the SPCA was available to ''take the cats away tomorrow'' [Wednesday], but Gardiner's counsel, Simon Claver, said Gardiner had approached a cat-fostering group which needed three weeks to find homes for the animals.
After the hearing, neighbours said they were pleased but were sceptical Gardiner would comply with the order.
''This has been going on for four years come June. We'll believe it when we see it,'' Katrina Robertson said.
Gardiner, who consistently hid her face from media cameras during the one and a-half day trial, stared ahead and showed no emotion as Judge Saunders gave his decision.
The prosecution called five witnesses - a council compliance officer and four neighbours - but Gardiner did not take the stand or call any witnesses.
In brief submissions, Mr Claver argued Judge Saunders should dismiss the charges because the section of the bylaw relating to when the council could issue a compliance notice was confusing, and because the section of the Health Act the prosecution was relying on related only to commercial premises, not homes.
Judge Saunders rejected those submissions, saying the notice to comply under the bylaw was correctly issued and the Health Act must refer to homes as well as many other types of premises.
He was satisfied from the evidence Gardiner had many cats on her property and her lack of control had created a nuisance for neighbours.
On the charge of breaching the bylaw he fined her $400 - the maximum penalty available is $500 - and ordered her to pay court costs of $130.
He also ordered her to pay $750 towards prosecution costs, saying it was fair she paid something.
Ratepayers and taxpayers had been ''hit with a double whammy'' as ratepayers were funding the prosecution and Gardiner was receiving legal aid for her defence, he said.
On the Health Act charge he ordered her to pay court costs of $130 and said the best outcome was for her to comply with the abatement order.
He warned if she did not comply, further charges could be laid and she could face non-compliance fees of $50 a day, plus a significant contribution towards prosecution costs.
Earlier in the day, neighbours gave evidence about their issues with the cats since Gardiner moved into Thurso St, northeast Invercargill, in June, 2011.
The issues included cats fighting, faeces deposited on their lawns and gardens, seedlings uprooted, cats spraying inside and outside homes, and cats entering homes and sleeping there or eating other pets' food.
Ms Robertson and another neighbour whose name was suppressed spoke of their cats becoming stressed when Gardiner's cats ganged up on them outside.
Ms Robertson's cat became so stressed it regularly coughed up fur balls, while the other neighbour and his wife decided to have their elderly cat put down.
A third neighbour, whose name was suppressed, said several neighbours decided to trap the cats one night, hiring traps from the council.
About eight were caught and taken to SPCA but she understood Gardiner got them all back.
She said Gardiner did not comply with a notice to reduce cat numbers.
''It was just so frustrating. We can't enjoy our property - our own property. And it's been going on for years.''
